Deep drilling control system



June 19, 1962 G. LOOCKE DEEP DRILLING CONTROL SYSTEM 2 Sheets-Sheet 2Filed Nov. 12, 1957 0 a W 3 1 w m 3 H m 3 3 5 B m M 3 w 2 3 L 3 W 3 0J 3a 3 L w I 3 L o f o O 1|! F f --I I E L L a I 0 c m 5 i 3 A 3 g 3 Wm H.Q 9 5 0 a A6 m w M e A 3 w 3 L 0 MJJ u 3 EN Inventor:

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GWWA W4 United States Patent Germany Filed Nov. 12, 1957, Ser. No.695,899 Claims prioritsy, application Germany Nov. 12, 1956 Claims. (Cl.17 -26) The present invention relates to deep drillings and moreparticularly to an electric control system for deep drills and deepdrilling operations.

Deep drillings particularly those for oil wells, are generally done by adrill bit fastened to the lower end of a drill rod. The latter is drivenby a motor at its upper end, the motor being stationed on the surface ofthe earth.

Recently, an improved drill has been devised, in which the motor ispositioned at the lower end of the drill rod above the drill bit. Theelectric motor directly impels the drill bit whereas the tubular drillrod does not revolve and is only used for removing the drillings fromthe drilling hole, generally by means of liquid passed through the drillpipe. The drill pipe is suspended into the drilling hole from a derrickand is progressively released in accordance with the advancement of thedrill bit in the earth.

The known drilling devices do not speed and efficiency of operation.

In particular, the drilling speed is not adjusted to its optimum degreeat any given moment.

The drilling speed (v), i.e. the speed at which the drill bit advancesvertically in the earth depends on a plurality of conditioning factors,as, for example, the nature and structure of the ground, the torque ofthe motor driving the drill, and the quantity of the flushing liquid(generally wash water) which is conveyed through the drill tube in orderto remove loose earth, rocks, etc., loosened by the drill bit.

In case of an elevated drilling speed a considerable amount of drillingshas to be removed from the drilling hole and hence the quantity of washfluid must be correspondingly great.

Of course, the total amount of the wash liquid cannot be increasedbeyond a certain 'amount in view of the limited capacity of the pump orthe cross section of the pipe conduits. If the drill speed is evenfurther increased, the amount of the wash liquid becomes insufiicientand is therefore incapable of removing the entire drillings. The drillbit may then get stuck in the loose, unremoved drillings and it may evenbreak.

It is therefore of paramount importance to adjust the drilling speed tothe available wash liquid, and to adjust the drilling speed to thevarious other above named conditioning factors, as the torque capacityof the motor, the structure of the earth.

It has already been suggested in the art to adjust the drilling speed byproviding a plurality, for example four, electric motors at the lowerend of the drilling rod, which can be switched on and on" together orseparately from a control desk above the ground, thereby changing thetorque with which the drill bit is impelled.

In the motor casing there is arranged a telephone or microphonedetecting the drilling sound and conveying the same to the control deskabove the ground, where a listening operator tries to discern from thequality of the received sounds if the drill bit operates in soft or hardground and correspondingly decides if and how many electric motors haveto be switched in or have to be switched oli, respectively, in order toadjust the drilling speed to the prevailing conditions in the drillinghole (see US. patent to Lord 1,666,461).

, It is quite obvious that this manner of control requires attain anoptimal 3,339,543 Patented June 19, 1962 great skill and experience onthe part of the operator and is still insufiicient and unreliable.

It is an object of the present invention to provide an automatic controlsystem for use with deep drills of the type having the motor mounted atthe lower end of the drill rod in the drill hole and directly impellingthe drill bit, with the drill rod remaining stationary, which controlsthe drilling operation of the deep drill so that at each moment of thedrilling operation the optimal drilling speed is obtained under theprevailing drilling conditions.

It is another object of the present invention to provide an automaticcontrol system for use with deep drills of the type having the motormounted at the lower end of the drill rod in the drill hole and directlyimpelling the drill bit, with the drill rod remaining stationary, whichis fully automatic and assures an elficient and reliable control in anuncomplicated manner.

It is a further object of the present invention to provide an automaticcontrol system for use with deep drills of the type having the motormounted at the lower end of the drill rod inthe drill hole and directlyimpelling the drill bit, with the drill rod remaining stationary, whichguarantees the greatest possible progress of the drilling operationwhile avoiding damage to the drilling equipment, and particularly themotor and the drill bit.

These objects are achieved by the automatic control system of thepresent invention for controlling deep drillings, in which the drillingis effected by a drill bit driven by an electric motor provided at thelower end of a drilling rod in the drill hole and in which the drill rodis suspended from a winch above the ground.

According to the present invention, the automatic control is effected byinterconnected electrical control systems automatically adjusting thedrilling speed to its optimal value, taking into consideration theprevailing drilling conditions.

The control system of the trol systems hereinafter identified as a, b,c.

The control system or controls the drilling speed so that the maximumvalue of the permissible torque of the motor driving the drill bit isnot exceeded.

In the control system b the drilling speed and the quantity of flushingliquid conveyed to the drilling hole are controlled and adjusted to eachother so that the necessary quantity of flushing liquid is supplied tothe drill hole without undue waste of flushing liquid.

The control system c envisages the situation in which the quantity ofthe flushing liquid cannot be increased and in which the flushing liquidis now kept at a constant level. The control circuit 0 renders themaximum amount of the flushing liquid, the control reference valuefactor which controls the drilling speed, so that no more drillings areproduced as can be removed by the maximum amount of flushing liquid,control system 0 also ensures that the permissible torque of the motoris not exceeded.

The invention will be better understood upon the following descriptionof the accompanying drawings, wherein FIGURE 1 is a schematic view of adeep drill of the.

type having the motor driving the drill bit disposed at the lower end ofthe drill rod in the drill hole;

FIGURE 2 is a schematic representation of the switching diagram of thecontrol systems a, b, c' of the control arrangement of the presentinvention;

FIGURE 3 is a schematic view of one embodiment of the controlarrangement for deep drills of the present invention.

Referring now to the drawings somewhat more in detail and turning firstto FIGURE 1, the drill rod 2 is suspended from the derrick 1 and bearsat its lower invention comprises the conend the electric motor 3 drivingthe drill bit 4. Since the drill rod 2 is suspended on the suspensionwire 5, the electric motor 3 and the drill bit 4 are relieved from someof the weight of the drill rod 2. The suspension wire 5 is guided over apulley 6 and a winch "7 and can be raised or lowered by the latter inaccordance with the drilling speed. Preferably, the winch 7 is driven bya motor. Flushing liquid is pumped into the drill rod 2 at its upper endby pump (not shown in FIG. 1) via the tube 8. The drill rod 2 does notrotate and remains stationary during the drilling. It is only used. forcar-rying the electric motor 3 and the drill bit 4 and as a conduit forconveying the flushing liquid to the drilling hole. This Wash liquid hasto remove the drillings from the hole.

The control system schematically shown in FIGURE 2 comprises the controlcircuits at, b, c, which will next be described.

The particular size and construction of the electric motor 3 determinesthe theoretical torque output which the motor can furnish at aparticular voltage, frequency and stator current. This theoreticaltorque is reproduced by the setting device it as a reference value. Theactual torque output of the motor 3 can be ascertained by measuringvoltage, frequency and stator current, and these measured values can beused to reproduce the torque; this is carried out in the transformingdevice 11. In other words, device It} produces a reference value, forexample a current indicative for the desired torque and device 11reproduces the actual torque as produced by motor 3.

The torque exerted by the drill bit, and hence the actual value of thetorque of the electric motor 3, depends to a great extent on the loadapplied to the drill bit. The torque of the electric motor 3 cantherefore be varied by turning the winch 7 in one direction or the otherso as to raise or lower, respectively, the drill rod 2, therebyincreasing or reducing, respectively, the pressure exerted by the latterupon the drill bit 4.

The second important factor is the drilling speed. This factor can beascertained from the speed v with which the suspension wire 5 isreleased from the winch. The latter speed can be easily determined bymeasuring the rotary speed of the pulley 6. A control valuecorresponding to the measured value of the drilling speed v is formed inthe transforming device 12.

A third important factor is the quantity of the flushing liquid. it ismeasured by a quantitative measuring device 13 an example of which isdisclosed in FIG. 3, elements 331, 332 to be explained later.

In the setting device it a predetermined DC. current is provided whichrepresents and corresponds to the reference control value of the torqueof the motor 3. The transforming device 11 furnishes a valueproportional to the actual value of the torque of the motor. This valueis preferably proportional to the active current of the motor in whichcase both voltage and frequency are also controlled. In the comparingdevice 14 an error signal is ascertained by comparing the referencevalue produced in the setting device it} and the actual value of thetorque of the motor supplied by the transforming device 11. Inaccordance with this error signali.e. the difference between thereference value and the actual value of the torque of the motor-theautomatic controller 15 is actuated which, in turn, controls the winch 7via the automatic control circuit (system) a in the following manner:

If the actual value of the torque of the motor 3 is too small, i.e.-less than the reference value, the winch is caused to turn in clockwisedirection so as to release an additional portion of the suspension wire5, thereby increasing the weight of the drill rod 2 and the motor 3 uponthe drill bit 4. Due to the increased pressure upon the drill bit, thetorque of the latter and the motor is also increased until the actualvalue of the torque has become equal to the reference value.

If the actual value of the torque is too great, i.e. greater than thereference value of the torque of the motor, the winch 7 is caused toturn in counterclockwise direction so as to reduce the weight of thedrill rod acting upon the drill bit 4. Consequently, the torque isreduced until actual value and reference value of the torque have againbecome equal.

In both instances the change of the torque of the motor varies the valueformed by the transforming device 11 correspondingly (see the doublearrow behind the winch 7 in the diagram of FIGURE 2).

The quantity of flushing liquid Q to be furnished by the pump 8 dependson the drilling speed v. A suddenly increasing drilling speed vindicates that the drill bit 4 has hit upon ground of a softer structureand therefore produces a greater amount of drillings than before. inthis situation the quantity Q of flushing liquid must be increased inorder to remove the greater amount of drillings and to prevent the drillbit from getting stuck in the loose gravel. The value of the drillingspeed v formed in the transforming device 12 is therefore used as acontrolling condition for adapting the amount of the flushing liquid tothis new situation. This is done by comparing in a device 17 the valuesupplied by the transforming device 13 representing the actual value ofthe quantity Q of flushing liquid with the value supplied by thetransforming device 12. The resulting deviation, which is also an errorsignal, actuates the automatic controller 17 thus inducing the latter toeffect a corresponding change of the amount of flushing liquid conveyedby the pump 8. (Control system b.)

If the drilling speed continues to increase, it may occur that themaximum conveying capacity of the pump and the conduits is reached. Itis therefore necessary to reduce the drilling speed down to a levelcorresponding to the maximum available quantity of flushing liquid. Thereduction of the torque of the drill bit, which is equivalent to areduction of the drilling speed, is effected by the automatic controlsystem c. As soon as the maximum value Q of the capacity of pump 8 isreached, a signal is sent by the maximum contact 8 to the pump 8. As thecontact 8 closes, the quantity of flushing liquid Q is now establishedas a controlling condition Whereas the drilling speed now becomes thecontrolled condition. The transforming device 12 measures the actualvalue of the drilling speed v and the actual value is compared with thedesired value of the drilling speed in the comparing device 16'. Theresulting deviation induces the automatic controller 16 to lower, viathe setting device 10, the desired value of the torque of the motor 3down to a level which can be considered assafe in View of the constantquantity of available flushing liquid.

The various control systems just described can be equipped withelectrically operated elements, or with hydraulic, electro-hydraulic orelectro-pneumatic elements. in the embodiment shown for illustrativepurposes in FIGURE 3 electrically operated control elements are used.

The following table shows the correlation between the elements of thecircuits illustrated in FIGURES 2 and 3 of the drawings:

FIGURE 2 FIGURE 3 Setting device 10. Field coil 317. Transforming device11. Field coil 315.

Counting device 310. Generator 309.

Quantitative measuring device 13. Comparing device 14. Automaticcontroller 15.

Measuring device 331. Amplidyne 314.

Direct current motor 311. Direct current generator 312. Field coil 313.

Field coil 321.

Field coil 325.

Generator 324.

Motor 323.

Switch relay 333. Potentiometer 334. Rectifier 335.

Comparator 16 Pump controller 17.

Comparator 17.

FIGURE 3 shows the derrick 301 with the drilling rod 302. The drill rod302 is suspended by suspension wires 305 running over pulleys 306. Atits lower end, the drill rod 302 bears the motor 303 and the drill bit304 driven by the motor 303.

The suspension wire 305 runs over the pulleys 306 communicating withwinch 307. By turning this winch, the drill rod 302 can be lifited orlowered at the desired speed corresponding to the drilling speed of thedrill bit. A special motor can be provided which is adapted to lift orlower the drill rod very slowly. Furthermore, there is provided a pump308 conveying the flushing liquid through the drill rod to the bottom ofthe drill hole.

A three-phase-current generator 309 supplies the necessary current tothe electric motor 303. In the power line between the generator 309 andthe motor 333 there is inserted a counting device 310 known per semeasuring current and voltage and forming a current impulseproportionate to the actual value of the torque of the motor 303. Seefor example: St'ztblein-Die Technick der Fernwirkanlagen,Oldenbourg-Berlin 1934, pages 30 to 34. This value, which corresponds tothe actual value, is fed to the coil 315 of generator 314 of theamplidyne type.

The winch 307 is driven by a direct current motor 311 fed by a directcurrent generator 312 having a field coil 313. Current is supplied tothis field coil by the above mentioned amplidyne 314. This amplidyne hasseveral field coils. One of its field coils, the above-mentioned fieldcoil 315, is excited by a current corresponding to the actual value ofthe torque of the electric motor 303.

The further field coil 317 is excited by a constant direct currentsource which corresponds to the desired value of the torque of theelectric motor 333. There is a contact blade 3332 connected in serieswith coil 317 and pertaining to a relay 333, to be explained later. Thetorque of the motor is obtained by calculation or by tests in a mannerknown per se. A field coil 318 of the amplidyne 314 is fed by anotheramplifying means (e.g. an amplidyne 319).

This amplidyne 319 has a field coil 320 actuated by a constant currentand a field coil 321 excited by a current depending on the drillingspeed. Thus, amplidyne 319 constitutes a comparator between a referencevalue (current in coil 320) and a speed responsive signal (current incoil 321). The constant value exciting the field coil 320 is the desiredvalue of the drilling speed and the value exciting the field coil 321 isthe actual value of the drilling speed. The current supply to coil 320is governed by a contact blade 333d, also pertaining to the said relay333 (infra).

The drilling speed is measured by a tachometer generator 322 coupledwith the pulleys 306. Tachometer generators of this type are disclosed,for example, in U.S. Letters Patent No. 2,889,475. The tachometer 322thus furnishes a direct current which is proportional to the rotatingspeed of the pulleys 306 and hence to the drilling speed. The voltage ofthe tachometer is fed to the field coil 321 of the amplidyne 319 via acontact blade 3330.

The pump 308 is driven by the motor 323 which, in turn, is supplied withcurrent by the generator 324. The field coil 325 of this generator isexcited by an amplidyne 326. This amplidyne 326 has several field coils.The field coil 328 is excited by a constant DC. voltage via contactblade 333a. The excitation of the field coil 329 depends upon the amountof the flushing liquid. The excitation of the field coil 330 dependsupon the drilling speed since this field coil is connected to thetachometer 322 via a contact blade 33311.

The amount of the flushing liquid conveyed by the pump is measured by asuitable measuring device 331 as, for instance, by a venturi meter. Thenumber of revolutions in the venturi meter is proportional to the amountof flushing liquid and measured by the tachometer 332, the voltage ofwhich is supplied to the field coil 329.

326 depends on the amplidyne a portion of the excitation of the exciteramount of flushing liquid conveyed by the pump 308. In other wordsamplidyne 326 constitutes a comparator for the two signals respectivelydeveloped in said coils 329 and 330 and the current flowing in coil 325can be considered an error signal resulting from the comparison of theflux in coils 329 and 330.

Furthermore, there is provided a threshold switch relay 333 controllingall of the contact blades 333a to 333a in the system shown in FIGURE 3,and operating as threshold or limit switch.

This switch relay 333 is actuated as soon as the pump 308 has reachedits maximum number of revolutions and hence the amount of flushingliquid cannot be further increased. This maximum number of revolutionscorresponding to the maximum conveying capacity of the pump 308 is adatum given and known by the construction of the individual pump. Acurrent corresponding to this maximum capacity of the pump is formed bythe potentiometer 334 which latter is connected with the switch relay333 via the rectifier 335. Under normal operating conditions the voltagecreated by the tachometer 332 counteracts the voltage of thepotentiometer 334. As long as the tachometer voltage is less than thevoltage of the potentiometer 334 the relay 333 is inactive. After thevoltage of the tachometer 332 has reached the fixed voltage at thepotentiometer 334, the relay 333 is actuated and the relay then opensall those contacts in FIG- URE 3 which are shown as closed (333b, 333a)and it closes all those contacts (333a, 3330, 333d) which are shown intheir respective opened positions. Accordingly, coils 321 and 320 areenergized and excite amplidyne 319 which now, in turn, energizes coil318. The current in the latter coil is now the reference value for thecurrent in coil 315 because upon opening of contact 333e, coil 3-17becomes ineffective.

A tachometer is described, for example, in Elektrische Messungmechanischer Grossen, Springer 1956, 4th edition, pages 198/ 199, and adevice for measuring the quantity of liquids is described therein onpage 210. A torque measuring device is described on pages 192/193, seealso the diagram 260.

An amplidyne which can be used for the purpose of the present inventionis described, for example, in U.S. Patent 2,247,166.

Consequently,

Operation The embodiment shown in FIGURE 3 operates in the followingmanner:

The actual torque as produced by the electric motor 303 is measured inthe counting device 310 and fed to the field coil 315. The referencevalue of the torque is given by the excitation of field coil 317. Thedeviation 1.e. the error signal which is the diflierence between the twovalues acts upon the motor 311 via the amplidyne 314 and the field coil313 of the generator 312. Hence,

the winch 307 is adjusted at such a speed that the maximum of theallowable torque of the motor will not be exceeded.

The flushing liquid which has to supplied by pump 308 is determined bythe drilling speed. If there is a greater drilling speed v; thisisindicative of the fact that the drill bit 308 has encountered softground and a greater quantity of drillings is obtained. Consequently,the amount of the flushing liquid must be increased correspondingly inorder to remove the increased amount of drillings so as to prevent thedrill bit from getting stuck in the drillings. The value of the drillingspeed .is measured by the tachometer 322 and a corresponding .directcurrent is supplied to the field coil 330 of the amplidyne 32 6. Theamount of the flushing liquid passing into the borehole is measured bythe tachometer 332 and a corresponding direct current is fed to thefield coil 329. The two factors are thus compared and adjusted to eachother in the 326 with a view to make, the driving motor 323 of the pumpturn with the required number of revolutions. The situation may occurthat the flushing liquid cannot be further increased in view of themaximum capacity of the pump 3% and the cross section of the conduit inthe drill rod 302.

The maximum amount of flushing liquid which can be conveyed by the pumpto the drilling hole is of course known at the time of installation ofthe entire system. A corresponding maximum value is formed in thepotentiometer 334. As soon as the voltage produced in the tachometer 332reaches this maximum value the reversing relay 333 responds and closesall contacts which had hitherto been opened and opens all contacts whichhad hitherto been closed. This means that also the contact 333a in thecircuit of the field coil 328 is closed. Thereafter the amplidyne 326 isconstantly excited. The contact 33317 in the circuit of the field coil339 is opened, i.e. there is no longer any influence of the tachometermachine 322 on the amount of flushing liquid conveyed by the pump 3&8.The amount of the flushing liquid now remains on the constant level Qwhich is expressed by a constant voltage supplied by the amplidyne 326and resulting in a constant number of revolutions of motor 323 and pump308.

As soon as reversing relay 333 reponds i.e. in case the maximum quantityof the available flushing liquid Q has been reached, contact 3330 whichis in the circuit of the field coil 321, and contact 333 of governingfield coil 329 are closed; both coils pertain to amplidyne 319. Thevoltage supplied by the tachometer 322 and corresponding to the drillingspeed now influences amplidyne 319. Simultaneously, contact 333e isopened and winding 317 is rendered ineflective so that winding 318 takesover for flux comparison in amplidyne 314 as stated above.

If the drilling speed deviates from the value represented by the currentin coil 328 there will be an error signal due to the flux comparison ofthe coils 320 and 321 and being effective in amplidyne 319 ascomparator. The output of amplidyne 319 resulting from this comparisonin turn is fed as a current to coil 3-1-8. This current in 318 producesa flux which is then compared with the flux developed by a current incoil 315, and amplidyne 3. 14 is thereby subjected to a second errorsignal resulting from such flux comparison. Arnplidyne 314 produces acorresponding output current in coil 313 to regulate the speed of motor311 so that the speed of motor 311 is brought back to the desired value.

It will be observed that this holds true only as long, as the torque ofmotor 311 (flux in coil 315) remains constant at a particular value. Ifthe actual torque decreases, the motor 311 is caused to increase thespeed of the winch and the drilling speed. An increasing drilling speedin turn causes elements 322, 3&9 and 314 to respond so as to decreaseagain the drilling speed. Thus, an approximately constant speed level isattained.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions and,accordingly, it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

What I claim is:

1. In combination with a deep drill including a drill rod, a drill bit,an electric motor mounted in the lower end of said drill rod and drivingsaid drill bit with said drill rod remaining stationary, a suspensionwire for said drill rod, a winch drivingly connected to said suspensionwire for raising and lowering said drill rod with said drill bit andsaid motor, a motor for driving said Winch, a pump for handling aflushing liquid through said drill rod into the bore hole so as toremove the drillings therefrom, an automatic control system comprising:electric circuit means responsive to the drill motor torque andproducing a corresponding electric output signal; electric .circuitmeans producing an electric reference value corresponding to a desiredtorque; measuring means for the drilling speed and producing an electricoutput signal corresponding to said drilling speed; measuring meansresponsive to the amount of fluid passing into said bore hole andproducing an electric output signal indicative of said amount of liquid;an electric threshold switch connected to said last mentioned measuringmeans and responding whenever a predetermined maximum amount of liquidpasses into the bore hole; a first electric comparator electricallyconnected to said two circuit means and producing a first electric errorsignal corresponding to the difference between said reference value andsaid torque output signal; control means electrically connecting saidcomparator and said winch motor and feeding said first error signal tosaid winch motor for governing its speed in response to said first errorsignal; a second electric comparator electrically connected to said twomeasuring means and producing a second electric error signalcorresponding to the difference between said two measuring signals;control means electrically interconnecting said second comparator andsaid pump motor for feeding said second error signal to said pump motorfor governing the flow of liquid in response to said second errorsignal, said threshold switch when responding deactivating theconnection between said speed measuring means and said second comparatorand deactivating said reference value producing means, when said maximumamount of liquid is reached; and circuit means being responsive to aresponse of said threshold switch and connected to said first comparatorfor establishing a drilling speed responsive reference value thereinWhenever said maximum amount of liquid is reached.

2. In combination with a deep drill including a drill rod and a pump forhandling a flushing liquid through said drill rod into the borehole soas to remove the drillings therefrom; a drill bit; an electric drillmotor mounted in the lower end of said drill rod remaining stationary; asuspension wire for said drill rod; a winch drivingly connected to saidsuspension wire for raising and lowering said drill rod with said drillbit and said motor; a motor for driving said winch; means for producinga measured value corresponding to the actual torque output of said drillmotor for a particular voltage current and frequency thereof; means forproducing a reference value for the torque of said drill motor at anygiven time; and control means connected to said winch motor and beingresponsive to the difference between said measured value and saidreference value of said drill motor to cause said winch to position saidsuspension wire with said drill rod and said drill motor upon said drillbit, thereby adjusting thetorque of said drill motor and said drill bit.

3. In combination with a deep drill including a drill rod, a drill bit,an electric drill motor mounted in the lower end of said drill rod anddriving said drill bit with said drill rod remaining stationary, asuspension wire for said drill rod, a control device comprising: a winchdrivingly connected to said suspension wire for raising and loweringsaid drill rod with said drill bit and said motor; a motor for drivingsaid winch; means for producing a measured value corresponding to theactual torque output 'of said drill motor for a particular voltage,current and frequency thereof; means for producing a reference value forthe torque of said drill motor at any given time; a comparator connectedto said two means and responsive to the difference between said measuredvalue and said reference value and being connected to said winch motorfor adjusting the drilling speed in response to said difference ofvalues; a pump for handling a flushing liquid through said drill rodinto the bore hole so as to remove the drillings therefrom; an electricmotor for said pump; means for measuring the flow of flushing liquidconveyed by said pump and producing an electrical signal correspondingto said flow of liquid; a tachometer generator connected to thesupension wire of said drill rod sensing the lowering speed of saiddrill bit and producing an electrical output signal corresponding tosaid speed; and

circuit means interconnecting said tachometer generator and said flowmeasuring means for combining said two signals and producing a commonoutput signal; and electric control means interconnecting said pumpmotor and said circuit means for causing control of said liquid flow inresponse to said common output signal so that the liquid flow increaseswith increasing drilling speed.

4. In combination with a deep drill including a drill rod, a drill bit,an electric drill motor mounted in the lower end of said drill rod anddriving said drill bit with said drill rod remaining stationary, asuspension wire for said drill rod, a control system comprising: a winchdrivingly connected to said suspension wire for raising and loweringsaid drill rod with said drill bit and said motor: a motor for drivingsaid winch; means for producing a measured value corresponding to theactual torque of said drill motor for a particular voltage, a currentand frequency thereof; means for producing a first reference value forthe torque of said drill motor at any given time; first control meansinterconnecting said winch motor and said two means being responsive tothe diiference between. said measured value and said reference value andgoverning the winch motor and drilling speed, thereby controlling theweight of said drill rod and said drill motor upon said drill bit, andalso controlling the torque of said drill motor and of said drill bit; apump for handling a flushing liquid through said drill rod into the borehole so as to remove the drillings therefrom; measuring means connectedto said pump and being responsive to the maximum flow of flushing liquidconveyed by said pump and deactivating said first reference valueproducing means upon occurrence of said maximum flow; means connected tosaid suspension Wire for measuring the drilling speed and producing anelectrical signal corresponding to said speed; and a normally inactivesecond electrical control means operatively connected to said speedmeasuring means and including means for supplying a second referencevalue to be compared with said speed responsive signal to generate athird reference value, said second control means being actuated inresponse to a signal corresponding to the maximum flow as measured bysaid flow measuring means, said second control means being furtherconnected to said first control means for feeding said third referencevalue thereto, thereby replacing said first reference value so as tolimit the speed of said winch motor and the drilling speed to a valuecorresponding to the maximum amount of flushing liquid.

5. An automatic control system for a deep drill including an electricmotor driven drill bit and means for nonrotatably suspending said motorin a bore hole, said system comprising: measuring means connected tosaid suspending means and being responsive to the drilling speed andproducing a corresponding electric output signal; a motor driven pumpfor conveying flushing liquid into the bore hole; measuring meansconnected to said pump and being responsive to the amount of liquidpumped into said bore hole and producing an electric output signalcorresponding to the said pumped amount of liquid; an electricalcomparator connected to said two measuring means and comparing said twooutput signals so as to form an error signal; a control meansinterconnecting said pump motor and said comparator so as to control theflow of flushing liquid in response to said error signal; an electricwinch motor drivingly connected to said suspending means for loweringsaid motor driven drill bit thereby determining the drilling speed; anormally inactive electric control circuit electrically interconnectingsaid speed measuring means and said winch motor for controlling thespeed of said winch motor in response to said drilling speed, saidnormally inactive control circuit, said winch motor with controlcircuit, and said drilling speed measuring means defining a closeablefeedback loop; and means connected to said liquid measuring means andbeing responsive to the maximum amount of liquid to be pumped, and whenresponding activating said control circuit for closing said feedbackloop.

References Cited in the file of this patent UNITED STATES PATENTS

